Story highlights

A special counsel and congressional committees have intensified their focus

The reality of impeachment: politics and public opinion count

Washington (CNN)Clandestine meetings. Special counsels. Congressional probes. Sound familiar? The constellation of headline-driving drama in today's news recalls the machinations that engulfed Presidents Richard Nixon and Bill Clinton for years of their respective tenures. Those episodes offer insight to understanding the still fresh events unfolding around the Trump administration.

Forty-three years ago this summer, the US Supreme Court forced President Richard Nixon to turn over White House tapes related to a break-in at the Democratic Party headquarters in the Watergate building. The unanimous decision, written by a chief justice appointed by Nixon, represented a judicial climax in the Watergate scandal and heightened the political momentum towards Nixon's Aug. 8 resignation.

The House judiciary committee voted on articles of impeachment three days after the ruling, and soon after Nixon stalwarts such as conservative Arizona Senator Barry Goldwater intervened to persuade the President to go. "There are only so many lies you can take," Goldwater told Republican colleagues on August 6, 1974. "Nixon should get his ass out of the White House -- today!"

Now, with energy building in the federal investigations into Russian interference with the 2016 presidential election and possible collusion by Trump campaign associates with Russian officials, comparisons to Nixon are growing. Special counsel Robert Mueller and congressional committees have intensified their focus on a June 2016 meeting at Trump Tower that Donald Trump Jr., Jared Kushner and Paul Manafort had with a Russian lawyer and others.

A Monmouth University poll released this week found that 41% of the public think Trump should be impeached and removed from office (53% disagree). That's a much larger share than supported impeachment for Nixon in July 1973 when much of the evidence related to Watergate emerged. At the time, 24% supported impeachment and 62% opposed it. By the first week of August 1974, Gallup reported that 57% said Nixon's actions were serious enough to warrant removal from office.

Read More

Yet, while the Watergate scandal and, to a lesser extent, the Bill Clinton impeachment efforts nearly 20 years ago provide loose templates for how the current controversy might evolve, much more must develop before it's evident whether this investigation would destroy Trump's presidency or constitute a short chapter on his overall tenure.

The bottom line is it depends on the evidence -- evidence that is now being collected in secret. And as was plain in the fates of Nixon and Clinton, congressional politics and public opinion matter.

President Donald Trump has deemed the Russia-related probe "the greatest witch hunt in American political history."

To last week's revelations that Trump Jr. met with a well-connected Russian lawyer to gain damaging information on Democratic presidential nominee Hillary Clinton, the President said it was politics as usual.

"My son is a wonderful young man. He took a meeting with a Russian lawyer, not a government lawyer, but a Russian lawyer," Trump said. "I think from a practical standpoint most people would have taken that meeting ... Politics isn't the nicest business in the world, but it's very standard, where they have information and you take the information."

Don't expect a quick conclusion

The Democratic National Committee burglary that began Nixon's downfall was June 17, 1972.

And Nixon's resignation came a year after nationally televised Senate hearings in 1973, during which his role in the Watergate cover-up emerged and the presence of a taping system -- which captured Oval Office conversations about the break-in -- was revealed.

In March 1974, several top aides, including former Attorney General John Mitchell, were indicted on conspiracy, obstruction of justice and other offenses.

The Clinton scandal also took years to develop.

Kenneth Starr, the special prosecutor, was appointed in 1994. His investigation expanded beyond a Whitewater land deal in the Clintons' home state of Arkansas to Paula Jones, a former Arkansas state employee who had sued Clinton for sexual harassment, and later to Monica Lewinsky, a White House intern with whom Clinton had an affair. Clinton was not impeached until late 1998.

Special counsel Mueller has yet to reveal any results of his Russia-related investigation or possible criminal charges. He was appointed in May after Trump fired FBI director James Comey, who had been overseeing the probe.

Comey later testified that Trump had urged him to stop pursuing the Russian connections of former national security adviser Michael Flynn.

The Comey firing recalled the October 20, 1973 "Saturday Night Massacre," when Nixon sacked then-Watergate prosecutor Archibald Cox. Attorney General Elliot Richardson and Deputy Attorney General William Ruckelshaus, refusing Nixon's order to fire Cox, resigned that same night.

Leon Jaworski took over as special prosecutor and continued to seek the White House tapes. In the July 24 Supreme Court opinion, Chief Justice Warren Burger said the public's right to evidence outweighed Nixon's claim of executive privilege: "The very integrity of the judicial system and public confidence in the system depend on full disclosure of all the facts."

CNN has reported that Mueller's investigators are following up on the meeting attended by Trump Jr., Manafort and Kushner as part of the broader investigation into Russian meddling. Mueller has asked the White House to preserve all documents related to the meeting.

The Senate intelligence committee and other congressional panels are also investigating and seeking the testimony of Trump Jr., Manafort and Kushner.

Across all fronts, investigators are looking for any Trump campaign involvement with the Russians.

How impeachment works

The Constitution does not address whether a president may be criminally prosecuted, and the Department of Justice has previously said that the president can be removed only through the impeachment process. In 1974, Nixon was not criminally charged; the grand jury named him as an unindicted co-conspirator.

The Constitution says grounds for impeachment are "treason, bribery, or other high crimes and misdemeanors." A simple majority is needed in the House for articles of impeachment, but conviction in the Senate requires a two-thirds majority (67 votes).

In Clinton's case, the Republican-run House passed two articles impeachment in December 1998 related to perjury and obstruction of justice. The Senate acquitted Clinton in February 1999, failing to reach the necessary two-thirds majority of votes required. (The only other American president to be impeached, Andrew Johnson, in 1868, was not convicted by the Senate either.)

Clinton remained relatively popular through the impeachment ordeal. His lowest approval rating in CNN/Gallup/USA Today polling from January 1998 through March of 1999 was 59%. For much of the time the Starr investigation was underway, his approval percentage remained high, in the 60s and 70s.

Politics matter

And that is the reality of impeachment: politics and public opinion count.

Gallup reported that 37% approve of Trump, 58% disapprove, per their daily tracking poll. Nixon had a 24% approval rating as he resigned, according to Gallup. House impeachment and Senate conviction seemed inevitable. Goldwater, a former presidential candidate and conservative bulwark, told Nixon he lacked the Senate votes for acquittal.

Today, Trump has the backing of leaders in the GOP-controlled House and the Senate. Any chance of impeachment appears remote.

A more salient question is whether pressure will build, from Mueller, congressional committees, the public, or even the courts, to alter the current dynamic.

Correction: This story was updated to reflect that President Andrew Johnson was impeached in 1868.